The invention relates generally to a cutting apparatus such as a circular saw assembly for cutting metal.
In a known form of cutting apparatus, the apparatus comprises a shaft for carrying the cutting tool, the shaft being axially displaceable relative to a support or bearing housing in which it is mounted, for the purposes of providing for a return stroke movement of the cutting tool after the cutting operation, without coming into contact with the material being cut. The apparatus has a hydrostatic shaft bearing arrangement which is operative both in the radial and in the axial direction, with a bearing flange which is non-rotatably connected to the bearing housing and which is provided on its inside and at one of its end faces with bearing pockets or recesses with capillary feed means leading thereto. The apparatus further has an annular piston which is arranged axially displaceably in an annular cylinder between a portion adjoining the other end of the bearing flange, being of smaller outside diameter, and the bearing housing. At its end which is towards a bearing ring which is non-rotatably connected to the shaft, the annular piston has bearing pockets or recesses with capillary feed means leading thereto, and, in the operative position of the cutting apparatus, the piston bears against the bearing ring, due to a hydraulic pressure which is applied to the opposite end thereof.
Cutting apparatuses of the above-indicated kind, which are used primarily in the working flow in production installations such as rolling mill trains, in the form of an integrated piece of equipment therein, are generally provided for the purposes of cutting up long portions of the rolled material, being either individual portions or a plurality of portions which are disposed in side-by-side arrangement in the cutting operation, and/or cutting off or cropping the ends of the blanks or unworked components which cannot be put to use. In that operation, the elongate portions of material are generally carried on conveyor means such as roller beds. The portions of material are positioned by suitable means in such a way that the location at which a cut is to be made is aligned with the cutting tool. The material is then clamped in position, and the actual cutting operation is subsequently carried out. After the cutting operation, particularly when using cutting tools which are tipped with a hard material such as a hard alloy or metal or carbide metal, it is necessary to have a space between the material being cut and the cutting tool, before the cutting tool performs its return stroke movement, in order to ensure that any chips or cutting waste or the like which is caught in the apparatus or on the material being cut does not cause damage to the cutting tool during the idle or return movement thereof, or give rise to undesired grooves or scoring at the locations at which the material has been cut.
If the apparatus is to produce a clean cut, it must provide a bearing support for the tool, which is as smooth as possible, during the cutting operation, and thus must have a stable bearing arrangement. In addition, there is the requirement that, after the cutting operation, the cutting apparatus and the material being cut can be moved away from each other for the return movement or idle movement of the cutting tool, but without releasing the material clamping action at both sides, as is required to give a good quality of cut. For that purpose, after the cutting operation or after the cutting stroke movement of the tool has been concluded, the material-clamping device which is disposed at a remote position from the mounting arrangement supporting the cutting tool may first be moved away from the cutting tool by a given distance, and then the shaft carrying the cutting tool, which is mounted displaceably in the bearing or support housing, may be displaced in the same direction after the cutting operation, approximately by half the above-indicated distance. The return stroke movement of the cutting tool can then take place, without touching the cut surfaces of the material which has been cut.
The shaft carrying the cutting tool, which is thus arranged to be axially displaceable in the apparatus, may be supported by rolling-type bearings, but it is also known to use hydrostatic bearing arrangements, for example of the general kind referred to in the opening part of this specification. In this context, hydrostatically supporting the shaft in a radial direction does not in principle give rise to any difficulties. The shaft is supported hydrostatically in the axial direction by virtue of a bearing flange which is non-rotatably connected to the bearing housing and which is provided on its interior with the hydrostatic bearing pockets or recesses which are provided for producing the radial support action, being provided at one of its ends with bearing pockets or recesses having capillary feed means leading thereto, to provide the axial bearing effect. As, to permit the cutting tool to perform its return movement, the shaft must be arranged to be axially displaceable, it is not possible for the shaft to be axially supported in the other direction by means of corresponding bearing pockets or recesses at the other side of the bearing flange. Instead of that, the bearing effect is produced by means of an annular piston which has bearing pockets or recesses with capillary feed means leading thereto and which is disposed in an annular cylinder. The annular cylinder is disposed between a portion of the bearing flange, which is of smaller outside diameter, and the bearing housing. During the cutting operation, the annular piston is subjected to a pressure in the annular cylinder, more specifically from the side thereof which is in opposite relationship to the face of the annular piston which has the bearing pockets or recesses. For the purposes of producing axial displacement of the shaft of the cutting tool, the pressure in the annular cylinder is reduced and then the shaft is displaced axially by means of a separate arrangement. For a fresh cutting operation, pressure is again applied in the annular cylinder to cause the annular piston to be moved back into the operative position in which the shaft is hydrostatically supported in the axial direction, at two oppositely disposed sides.
Therefore, the function of the annular piston in the above-indicated arrangement is to produce or permit an axial hydrostatic shaft support action in the operative position of the cutting apparatus. For that purpose, the annular piston is fitted in the annular cylinder with a clearance of such a magnitude that it cannot jam therein. The clearance is sealed by suitable sealing rings. A disadvantage in that respect is that the bearing flange which is non-rotatably connected to the bearing housing cannot carry radial bearing forces in the region of the annular cylinder or annular piston. Therefore, the above-mentioned bearing flange which is designed at its inside and at one of its side or end faces to provide a radial and an axial hydrostatic bearing support action respectively, must be so dimensioned that it is capable of carrying all radial bearing forces which occur in that area. That means that the bearing arrangement is of considerable volume, which is a disadvantage in particular in regard to the amount of space that it occupies.